This bug: https://bugs.kde.org/show_bug.cgi?id=376347 has been fixed in Qt 5.8+ but it is still existing in KDE neon LTS User edition which has Qt 5.7.1 Please backport the patch for it. Thankyou.
Have you confirmed that the application that uses "kdialog" has been updated to use the correct parameters? If not, it still will not work, even with a newer Qt.
we also don't have a way to easily build qt 5.7 packages now so it's unlikely to be changed
If you can provide the information requested in comment #1, please add it.
No response, changing status. If you have new information, please add a comment.